Artifacts when using Gouraud or Phong interpolation

I am getting odd artifacts when looking at a 3D OBJ with vtk8.2 (even though we did not see this in our tool using vtk6.3). When I choose flat shading it looks fine (but we really want the option to show both as before). Any thoughts on what may be causing this?

It looks like some of the triangles are not oriented properly. You may be able to fix it using vtkPolyDataNormals. How did you generate this polydata?

I agree - but things looked just fine using vtk6.3.

I accidentally ran this with a 8.90 build of vtk earlier, so I’m working on getting 8.2 built so I can test that way.

This polydata was generated by another tool (I can’t say too much since the work is proprietary).